The present invention relates to measuring a property in a downhole apparatus.
More particularly, the various embodiments of the invention are directed to measuring incremental torque between sensors and using this information to improve drilling practices.
In downhole drilling, it has become commonplace to include in the downhole apparatus one or more logging tools. This may include any number of logging-while-drilling (LWD) and measuring-while-drilling (MWD) tools, which generally have mechanical apparatuses and electrical circuits to perform specific tasks.
As those skilled in the art know, the operating environment experienced by the logging tools is very harsh. By virtue of the tools being part of the downhole apparatus, the tools experience relatively high accelerating forces due to vibration of a drill bit cutting through downhole formations. Some parameters can be measured downhole and transmitted to the surface, thereby providing a feedback system, which improves drilling efficiency and downhole tool reliability. The torque and vibration experienced may exceed specified ranges for some components that make up the downhole apparatus, thus reducing the life span of any particular electrical or mechanical device.
These problems benefit from a method for updating and/or measuring the downhole torque on the downhole apparatus and transmitting this information to the surface to improve real-time operations. A common method currently used today for measuring downhole torque utilizes strain gauges. These devices require a lengthy and complex calibration process in order for them to properly measure the torque applied to the downhole devices. Even with this calibration process these gauges drift over time causing error with the measurements and must be periodically recalibrated.